The present invention relates to an electromagnetic actuating device. For example, such devices are known from German Utility Model 201 14 466, and are suitable for numerous actuating devices. A known application for such a device involves camshaft adjustment; the slide or plunger unit connected with the movable armature unit here acts on a camshaft of an internal combustion engine, thereby creating a desired adjustment functionality.
It is precisely within the context of an internal combustion engine or similar field of application that reliable operation becomes especially critical, wherein the special environmental conditions (high temperature, vibration, potentially frosty engine) can lead to occasional malfunctions, which have to be reliably detected. Correspondingly, so-called reset acquisition technologies are known from prior art for electromagnetic actuating device, wherein an induction signal of the armature unit moving in accordance with the camshaft position that was acquired and evaluated with the coil unit in a deenergized state is evaluated on the terminals of the coil unit. For example, DE 10 2006 035 225 A1 of the applicant shows this type of device.
However, the disadvantage to this technology in conjunction with other similar approaches from prior art not delved into in any greater detail here is that a malfunction can only be ascertained from a respective terminal signal with difficulty, which accordingly makes downstream evaluation electronics complicated and itself prone to failure in turn. Add to the above the disadvantage that this known induction technology can by principle only detect a movement by the plunger or armature unit, but not a respective plunger position; in particular, means for evaluating an induction coil voltage do not make it possible to reliably acquire a (standing) end position of the plunger, for example as it engages into the camshaft.
Accordingly, Utility Model Application 20 2009 006 940 of the applicant, which had not yet been public at the time of the present application, alternatively proposes that a coil voltage (induced by the permanent magnet unit) for acquiring the position of the armature be measured by providing stationary sensors (as magnetic field detecting means) in a housing or carrier unit of the actuating device, which act in conjunction with the permanent magnet means in a magnetically detecting manner, and output an accompanying magnetic field detection signal for further processing in response to a movement or position of the permanent magnet means (for example, corresponding to a movement or position of the armature unit). This signal is initially independent of an energized or non-energized state of the coil unit, and in particular also independent of a moving or idle situation of the armature, as illustrated by FIG. 9 for the drawn upon internal prior art from this utility model application: a housing unit (not shown) incorporates a stationary coil unit 10, which is formed around a stationary core 12. Mounted so that it can move in an axial direction (i.e., in the longitudinal direction on FIG. 9) relative to these stationary units is an armature unit 14 fitted with a plunger unit 16, whose engaging end 18 is designed in an otherwise known manner for interacting with a groove of a camshaft adjuster.
The armature unit 14 exhibits a (disk-shaped) permanent magnet unit 20, which is axially magnetized in the manner depicted, and situated opposite the core unit 12 in such a way that, in response to energizing the coil unit 10, the armature unit 14 in conjunction with the fitted plunger unit (held on the latter rigidly or detachably by the retaining force of the permanent magnet unit 20) is moved in an axial direction (i.e., downward on FIG. 9).
In order to realize the position detection, the permanent magnet unit 20 in this internal prior art has allocated to it a stationary sensor unit 22 (suitably provided in the housing not shown on the figures), which detects the permanent magnetic field and, realized as a Hall sensor, for example, can acquire this magnetic field and its change and relay it to a subsequent electronic evaluation by moving the armature unit 14.
As a result, this solution is able to overcome the principle-related disadvantages of the published prior art discussed above.
However, improvements are needed even for the kind of solution that was generically and schematically depicted based on FIG. 9 and must then of course be specifically configured to suit the individual case. The idealized state of the schematic representations on FIG. 10a (donned state of armature unit 14, only its permanent magnet disk (20) is shown) or on FIG. 10b (removed state of armature unit) of the schematically depicted coil unit 10 with core 12 show that the sensor unit 22 can effectively arrive at a good positional differentiation via a respectively varying field progression 21 of the permanent magnet unit 20 relative to the fixed sensor unit 22 (wherein the schematic signal diagram according to FIG. 10b in this regard also illustrates the progression of movement in terms of the drop relative to the level on FIG. 10a).
However, taking into account a coil field always present when the coil unit 10 is being energized (see field lines 11 in this regard), it turns out that the latter can cause the sensor unit 22 to malfunction when overlapped. This is because in particular the magnetic field lines of the coil field 11 overlap a possible detection state in the deenergized state (FIG. 11b) of the armature unit, so that this armature position might not be correctly detected by the sensor unit 22 in a case where energized.
Known from DE 10 2008 019 398 A1 is an electromagnetic actuating device with an armature unit that can be driven along or parallel to the axial direction in response to energizing a stationary, axially aligned coil unit, and is designed to interact with a slide and/or plunger unit extending in the axial direction, wherein permanent magnetic means are provided on and/or in the armature unit and/or the slide or plunger unit, and the coil unit and armature unit are at least partially accommodated in a housing or carrier unit, wherein the carrier unit has allocated to it stationary magnetic field detecting means that are designed for contactless magnetic interaction with the permanent magnetic means and configured in such a way that an axial position of the armature unit and/or the slide or plunger unit can be electronically ascertained in an energized and non-energized state of the coil unit by evaluating a magnetic field detection signal of the magnetic field detecting means, and the coil unit has allocated to it magnetic flux-directing means in such a way that it can dissipate a magnetic coil field generated by the coil unit away from the magnetic field detecting means and/or weaken it relative thereto.
With respect to further prior art, we refer to DE 199 35 428 C1 as well as U.S. Pat. No. 4,690,371.
Therefore, the object of the present invention is to improve the detection characteristics of a generic device that additionally exhibits stationary magnetic field detecting means for interaction with permanent magnet means moved by armature motion so as to detect position and movement, in particular to overcome any damaging influence by a magnetic coil field.